Hi,
Very clearly, a lot of my best images were shot on 12 MP APS-C. I normally print at A2 (16"x23") size and very good prints are possible from 12 MP. I would share the view that something like 20 MP is enough for A2 size prints, and that is the largest possible from desktop printers and cut sheet paper.
I have a couple of reasons striving for high MP, one reason is that I occasionally print larger than A2. I would feel that 39 MP has benefits printing A1 (23"x33").
The other reason is really making the best use of lenses. If a lens outperforms the sensor the sensor will produce artefacts. Almost any decently build lens outresolves almost any sensor in the center and in point of best focus, thus causing artefacts.
There are four ways around this:
- Add an OLP filter cutting resolution to avoid colour aliasing. Most OLP filters still leave a lot of monochrome aliasing.
- Stop down enough to reduce sharpness enough to avoid aliasing.
- Making the pixels small eough to reduce aliasing.
- Be happy with aliasing and call it microcontrast. Aliasing will always create fake detail, but it may not be obvious, it may just look real. In real world, observers object to colour aliasing.
From my experience it takes around f/16 to get almost aliasing free images on a non OLP filtered 6.8 micron sensor. So from that the largest aliasing free aperture on non OLP filtered 135 full frame sensors would be:
MP | Pixel pitch | Aliasing free aperture |
24MP | 6 | f/14 |
36 | 4.7 | f/11 |
54 | 3.8 | f/9 |
Now, almost all 24x36 and APS-C sensors are OLP filtered, up to 24 MP. Tendency is to drop OLP filtering at 36 MP for full frame and at 24MP for APS-C.
Attached is a screen dump of two images I shot yesterday, the second row is downscaled, note that downscaling introduces aliasing, too. The resizing was done in Image Magick (left) and Photoshop (right)
6.8 micron non OLP | 3.8 micron (OLP?) |
3.8 Micron Image Magick | 3.8 Micron Photoshop |
My take is that small pixels are necessary for correct rendition with good lenses. But, admittedly,
this may play a lesser role in real world photography. On the other hand, why buy expensive lenses if we don't make best use of them?
Best regards
Erik
IMO 20 mp is plenty unless you plan on making a large print. Something that is less and less demand now as the instant gratification generation moves to Facebook, Instagram etc.
I am done with the chase.
Paul